Weak signal reading circuit

Abstract

The embodiment of the invention discloses a weak signal reading circuit comprising a chopper amplifying circuit. The chopper amplifying circuit comprises a first chopper, a second chopper, a third chopper, a fourth chopper, and a first operational amplifier. The input end of the first chopper is connected with a weak signal. The output end of the first chopper is connected with the input end of the first operational amplifier via the second chopper. The output end of the first operational amplifier is connected with the input end of the fourth chopper via the third chopper. The output end of the fourth chopper is connected with a first filter circuit. The first chopper and the fourth chopper are controlled by a first chopping signal. The second chopper and the third chopper are controlled by a second chopping signal. The frequency of the first chopping signal is lower than that of the second chopping signal. The weak signal reading circuit may decrease offset voltage due to chopping ripples, reduces influence of noise and the offset voltage on the reading of the weak signal, increases the signal-to-noise ratio of a signal and the precision of a signal processing system.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a weak signal readout circuit. Background technique [0002] In today's era of advanced technology, sensors are widely used in industrial control, medical treatment, agriculture, and national defense and military fields. With the rapid development of integrated circuit technology, an important development trend of sensor technology is to realize the monolithic integration of sensors and their readout circuits. Due to the small amplitude and low frequency of the weak signal output by the sensor, it is easily affected by non-ideal factors such as environmental noise and offset voltage. Therefore, it is necessary to use a high-performance readout circuit to process the weak signal output by the sensor, amplify the weak signal into a signal that is easy to measure, and remove the influence of non-ideal factors such as environmental noise and offset voltage, and improve t...

AI Technical Summary

Problems solved by technology

Since the switching device in the first chopper 100 is turned on, there will be channel charge in the channel of the switching device, and the moment the switching device is turned on or off, the channel charge flows into or out of the switching device, that is, the charge of the switching device Injection effect, will introduce error, cause chopper ripple, make operational amplifier 200 output larger offset voltage

Moreover, since the difference between the frequency of the offset voltage and the frequency of the weak signal is very small, it cannot be filtered by the low-frequency filter 400, forming a residual offset, such as figure 2 as shown in (d)

At this time, the signal processed by the existing weak signal readout circuit has a low signal-to-noise ratio, which affects the detection and readout of weak signals, and the accuracy of the signal processing system is poor.

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